Adsorption refrigerating device

ABSTRACT

An adsorption refrigeration device having an evaporator containing a refrigerant liquid that evaporates under the effect of a depression and an adsorbent capable of fixing the vapors (V) of the refrigerant liquid. The adsorbent is in contact with a heat exchanger containing a cooling liquid that evaporates when the adsorbent (205) is heated, and the heat exchanger includes at least one aperture to the outside atmosphere constituted by at least one hole that limits the flow rate of the vapor of the cooling liquid.

The present invention relates to a device for refrigeration byevaporation and adsorption, whose principle consists in evaporating aliquid under the effect of a depression sustained by adsorption of thevapors of said liquid. It is the evaporation of this refrigerant liquidcontained in an evaporator (a chamber, cavity or the like) that promptsa cooling in the vicinity of the evaporator. Another chamber, containingadsorbent material, is generally connected to the evaporator.

The principle of refrigeration by evaporation of a refrigerant liquidand adsorption of vapor of this liquid has undergone numerousdevelopments, both for cyclical systems (with regeneration of adsorbentsby heating) and for single-use systems.

In all these devices, the adsorption is accompanied by heat dissipationin the adsorbent leading to a rise in temperature which it is sought tolimit by discharging a part of this heat.

The cyclical devices generally comprise adsorbents connected to heatexchangers which firstly discharge of the heat dissipated by theadsorbents during the adsorption reaction of the refrigerating liquidvapors and secondly heat these adsorbents to regenerate them.

In the case of single-use devices, the U.S. Pat. No. 4,759,191 proposesto limit the rise in temperature by the additionn to the adsorbents, ofdifferent materials, especially materials having a solid-liquid phasechange between 30° C. and 70° C. To obtain a significant effect, it isnecessary however to have a large quantity of solid-liquidphase-changing materials (about twice as much as the adsorbents). ThisU.S. Pat. No. 4,759,191 also mentions the possibility of using aliquid-gas phase-changing material as well as adsorbent temperatures ofup to 100° C. or even 110° C. However, the constraints related to theimplementation of such a device are not analysed.

The aim of the present invention is to overcome the drawbacks of theprior art.

The most efficient way to limit the rise in the temperature of theadsorbent is to remove the calories by water evaporation, for the latentheat of water is very high (45KJ per mole, namely 18 g of water).However, for fast evaporation, the water should be brought to boilingpoint. This entails a potential risk of scalding injuries.

To avert this risk, the present invention proposes to associate meanswith the adsorbent to bring down the temperature of the released vapor.

According to the invention, a heat exchanger containing a cooling liquid(preferably liquid water) is placed in thermal contact with theadsorbent. This heat exchanger has at least one aperture to the outsideatmosphere constituted by one or more small holes that limit the flowrate of the water vapor that might escape. This hole or these holesfurthermore give rise to an adiabatic expansion or pressure reduction ofthe pressurized water vapor so as to reduce its temperature when itescapes outwards.

The invention relates more particularly to an adsorption refrigerationdevice comprising an evaporator containing a refrigerant liquid thatevaporates under the effect of a depression and an adsorbent capable offixing the vapors of the refrigerant liquid, characterized in that theadsorbent is in contact with a heat exchanger containing a coolingliquid which evaporates during the heating of the adsorbent, said heatexchanger containing at least one aperture to the outside atmosphereconstituted by at least one hole that limits the rate of flow of thevapor of the cooling liquid

According to one characteristic, the cooling liquid undergoes adiabaticexpansion through said hole or holes so that its temperature is loweredwhen it escapes outwards.

According to one characteristic, the lowering of the temperature of thevapor is greater than or equal to 35° C.

According to a preferred embodiment, the cooling liquid comprises water.

According to another characteristic, the adsorbent is a zeolith.

According to one embodiment, the refrigerant liquid is water.

According to another embodiment, the refrigerant liquid is an alcohol.

According to one embodiment, the cooling liquid comprises an aromaticadditive releasing a sensation of freshness.

The particular features and advantages of the invention shall appearmore clearly from the following description, given by way of anillustrative and non-exhaustive example, made with reference to theappended drawings, of which:

FIG. 1 is a drawing of the device according to the invention in asingle-use application;

FIG. 2 is a diagrammatic view in longitudinal section of a portion A ofthe device according to the invention shown in FIG. 1.

The device according to the invention is designed to be associated atleast with one evaporator containing a refrigerant liquid L capable ofevaporating under the effect of a depression. The vapors V of thisliquid L are adsorbed by an adsorbent 205. This association is describedwith reference to FIG. 1.

A block of adsorbents 205 is connected to an evaporator 2 constituted byan airtight cavity containing a refrigerant liquid L. A communicatingdevice 50, consisting of a delidding means or a valve for example, isused to activate and then maintain the adsorption of the vapors V of therefrigerant liquid L.

The refrigerant liquid L is preferably water but it may also be analcohol (such as methanol or ethanol).

The adsorbent 205 is preferably a zeolite. For example, it is a zeolite13x or zeolite 4A made up of fine powder (with a grain size of somemicrons to some tens of microns) mixed with a binder (a clay, forexample kaolinite), and water to give a thick paste. This paste is thenshaped, dried and cooked under vacuum at about 350° to eliminate all thewater bound in the zeolite. The adsorbent is then kept in anvacuum-tight state.

The adsorption of the vapors V of the refrigerant liquid L prompts theheating of the adsorbent 205, thus limiting its efficiency. The mostefficient way to discharge the calories released by the adsorbent 205 isby water evaporation. However, for fast evaporation, the water must becarried to boiling point. This raises a potential risk of scalding.

The present invention proposes means to bring about a lowering of thetemperature of the released vapor.

According to the invention, a heat exchanger 220 containing a coolingliquid L′ is placed in thermal contact with the adsorbent 205. This heatexchanger 220 has at least one aperture 275 into the outer atmosphereconstituted by one or more small holes that limit the flow rate of thevapor V′ that can escape. This hole or these holes furthermore prompt anadiabatic pressure reduction of the vapor V′ under pressure so as tolower the temperature when it escapes outwards.

According to one possible embodiment, the assembly constituted by theadsorbent 205 and the heat exchanger 220 is closed by a lid 270 (made ofmetal such as aluminium for example). This lid 270 may have one or moreholes 275 whose diameter is limited in order to provide for an adiabaticpressure reduction of the vapor V′ of the cooling liquid L′.

According to a preferred embodiment, the cooling liquid L′ compriseswater.

According to one mode of implementation, it is possible to provide foran additive to the cooling liquid L′ which adds an artificial aroma tothe heated vapors V′ released outwards. This artificial freshness, basedon eucalyptus or watermelon for example, advantageously produces asensation of freshness.

During the operation of the device, the heat released by the adsorbent205 prompts the evaporation of the cooling liquid L′ and an increase inthe pressure of vapor V′ inside the heat exchange 220. When thepressurized vapor V′ escapes through the small-diameter hole or holes275, it undergoes adiabatic expansion or pressure reduction which lowersits temperature.

The extent of the drop in temperature of the vapor V′ escaping outwardsis all the greater as the flow rate of vapor V′ is high. This isbecause, in this case, the pressure in the exchanger 220 is high and thepressure reduction is great.

The table of numerical values here below illustrates the lowering of thetemperature of the vapor V′ discharged into the outside atmosphereduring the working of the device.

Thus, for example, for an overpressure of one bar, the temperature ofthe vapor V′ in the exchanger 220 rises to 120° C. but, after pressurereduction through the hole or holes 275, the temperature of thedischarged vapor is no more than about 55° C.

This overpressure may be achieved, for example, by a flow rate of vaporV′ of 0.1 g/sec through a hole with a section of 0.4 mm².

The cooling by adiabatic expansion or pressure reduction is governed bythe following physical law:$\frac{T_{2}}{T_{1}} = \left( \frac{P_{2}}{P_{1}} \right)^{\frac{\gamma - 1}{\gamma}}$

where the pairs (T₁,P₁) and (T₂,P₂) are the temperatures and pressuresbefore and after pressure reduction.

And where γ is the isentropic constant,

-   -   γ=1.35 for H2O at 100° C., (γ−1)/γ=0.259

Temperature in Pressure P₁ in the exchanger the exchanger Temperatureafter (° C.) T₁ (bar) expansion (° C.) T₂ 100 1 100 105 1.2 87 110 1.478 115 1.7 65 120 2 55 125 2.3 48

The following table illustrates the cooling capacity obtained as afunction of the overpressure caused.

The vapor pressure as a function of the temperature is taken from theHandbook of Chemistry and Physics, 80th edition.

The flow rates of the table correspond to a hole with a diameter of 1 mm(0.8 mm2) (Flowmaster code). The flow rate of vapor V′ is proportionalto the surface area of the hole, and the cooling capacity isproportional to the flow rate (latent heat of vaporization of water).

Flow rate T (° C.) P (bar) g/sec P (Watt) 200 15.53 1.62 4005 190 12.541.33 3325 180 10 1.05 2625 170 7.91 0.81 2025 160 6.17 0.63 1575 1504.75 0.48 1200 140 3.61 0.36 900 130 2.70 0.27 675 120 1.98 0.20 500 1151.69 0.17 425 112 1.53 0.15 375 110 1.43 0.134 335 108 1.33 0.12 300 1061.24 0.10 250 104 1.16 0.082 205 102 1.08 0.060 150 100 1

1. An adsorption refrigeration device comprising: an evaporator containing a refrigerant liquid that evaporates under the effect of a depression; an adsorbent capable of fixing the vapors of the refrigerant liquid; a heat exchanger in contact with said adsorbent and containing a cooling liquid that evaporates when the adsorbent is heated; and at least one aperture to the outside atmosphere provided in said heat exchanger and comprising at least one hole that limits the flow rate of the vapor of the cooling liquid.
 2. A device according to claim 1, wherein the vapor of the cooling liquid undergoes adiabatic pressure reduction through said at least one hole so as to lower the temperature when it escapes outwards.
 3. A device according to claim 2, wherein the lowering of the temperature of the vapor is greater than or equal to 35° C.
 4. A device according to claim 1, wherein the cooling liquid comprises water.
 5. A device according to claim 1, wherein the adsorbent is a zeolite.
 6. A device according to claim 1, wherein the refrigerant liquid is water.
 7. A device according to claim 1, wherein the refrigerant liquid is an alcohol.
 8. A cooling device claim 1, wherein the cooling liquid comprises an aromatic additive.
 9. An adsorption refrigeration device comprising: an evaporator containing a refrigerant liquid that evaporates under the effect of a depression; an adsorbent capable of fixing the vapors of the refrigerant liquid; a communicating device that allows the vapors of the refrigerant liquid to reach the adsorbent; a heat exchanger in contact with said adsorbent and containing a cooling liquid that evaporates when the adsorbent is heated; and at least one aperture to the outside atmosphere provided in said heat exchanger and comprising at least one hole that limits the flow rate of the vapor of the cooling liquid.
 10. A device according to claim 9, wherein the vapor of the cooling liquid undergoes adiabatic pressure reduction through said at least one hole so as to lower the temperature when it escapes outwards.
 11. A device according to claim 10, wherein the lowering of the temperature of the vapor is greater than or equal to 350°C.
 12. A device according to claim 9, wherein the cooling liquid comprises water.
 13. A device according to claim 9, wherein the adsorbent is a zeolite.
 14. A device according to claim 9, wherein the refrigerant liquid is water.
 15. A device according to claim 9, wherein the refrigerant liquid is an alcohol.
 16. A device according to claim 9, wherein the refrigerant liquid is an alcohol.
 17. A cooling device claim 9, wherein the communicating device is a valve. 